In racket sports, it is important that the player be able to determine a tension factor of the strings in the racket.
Today, the only way to ensure that a racket has a specific tension is to restring the racket to the desired tension. As the racket is used, the strings stretch and the tension changes over a period of use. The tension may also change with changes in ambient temperature and humidity.
Obviously, different sports are played with rackets having different sized heads and also in recent years, the size of tennis racket heads has been varied so that there is no standard size for tennis rackets at the present time. This requires a measuring device which provides a uniform test area and can be quickly and easily applied to the face of rackets used in any racket sport to determine a tension factor in the strings.
Also, the compressibility of the game balls is very important to the players. The only way to determine the compressibility of balls is to squeeze them manually or bounce them such as is done frequently. Players customarily discard balls after relatively short intervals of play an open new balls to ensure that the balls have full specification internal pressure as well as a uniform condition of the outer cover surface, and thereby ensure uniform performance during play.